Abstract

Cannabis contains various cannabinoids, two of which have almost opposing
actions: Δ9-tetrahydrocannabinol (Δ9-THC) is psychotomimetic,
whereas cannabidiol (CBD) has antipsychotic effects. Hair samples were
analysed to examine levels of Δ9-THC and CBD in 140 individuals. Three
clear groups emerged: `THC only', `THC+CBD' and those with no cannabinoid in
hair. The THC only group showed higher levels of positive schizophrenia-like
symptoms compared with the no cannabinoid and THC+CBD groups, and higher
levels of delusions compared with the no cannabinoid group. This provides
evidence of the divergent properties of cannabinoids and has important
implications for research into the link between cannabis use and
psychosis.